From: Robin Gong <yibin.gong@nxp.com>
To: Guenter Roeck <linux@roeck-us.net>,
"wim@linux-watchdog.org" <wim@linux-watchdog.org>,
"shawnguo@kernel.org" <shawnguo@kernel.org>,
"s.hauer@pengutronix.de" <s.hauer@pengutronix.de>,
"festevam@gmail.com" <festevam@gmail.com>
Cc: dl-linux-imx <linux-imx@nxp.com>,
"kernel@pengutronix.de" <kernel@pengutronix.de>,
"linux-watchdog@vger.kernel.org" <linux-watchdog@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v1] watchdog: imx2_wdt: clear WDOG_HW_RUNNING before suspend
Date: Wed, 12 May 2021 11:34:37 +0000 [thread overview]
Message-ID: <VE1PR04MB66889A576AD92D4D789199D489529@VE1PR04MB6688.eurprd04.prod.outlook.com> (raw)
In-Reply-To: <d5364293-8cba-0d39-aa45-a55c5d6d2af6@roeck-us.net>
On 2021/05/11 11:59 Guenter Roeck <groeck7@gmail.com> wrote:
> On 5/11/21 4:20 AM, Robin Gong wrote:
> > Since watchdog_ping_work is not freezable so that it maybe scheduled
> > before imx2_wdt_resume where watchdog clock enabled, hence, kernel
> > will hang in imx2_wdt_ping without clock, and then watchdog reset
> > happen. Prevent the above case by clearing WDOG_HW_RUNNING before
> > suspend, and restore it with ping in imx2_wdt_resume.
> >
> > Signed-off-by: Robin Gong <yibin.gong@nxp.com>
> > ---
> > drivers/watchdog/imx2_wdt.c | 8 ++++++++
> > 1 file changed, 8 insertions(+)
> >
> > diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
> > index b84f80f..d3751e9 100644
> > --- a/drivers/watchdog/imx2_wdt.c
> > +++ b/drivers/watchdog/imx2_wdt.c
> > @@ -357,6 +357,13 @@ static int __maybe_unused
> imx2_wdt_suspend(struct device *dev)
> > */
> > __imx2_wdt_set_timeout(wdog, IMX2_WDT_MAX_TIME);
> > imx2_wdt_ping(wdog);
> > +
> > + /*
> > + * clear WDOG_HW_RUNNING to prevent watchdog_ping_work
> running
> > + * before imx2_wdt_resume where clock enabled, otherwise kernel
> > + * will hang and watchdog reset happen then.
> > + */
> > + clear_bit(WDOG_HW_RUNNING, &wdog->status);
> > }
> >
> > clk_disable_unprepare(wdev->clk);
> > @@ -386,6 +393,7 @@ static int __maybe_unused imx2_wdt_resume(struct
> device *dev)
> > if (imx2_wdt_is_running(wdev)) {
> > imx2_wdt_set_timeout(wdog, wdog->timeout);
> > imx2_wdt_ping(wdog);
> > + set_bit(WDOG_HW_RUNNING, &wdog->status);
> > }
> >
> > return 0;
> >
> I really don't like this; it depends on assumptions how the watchdog core
> works, and it misuses WDOG_HW_RUNNING to indicate that the clock is
> stopped (or that the driver is in suspend mode).
>
> If ping doesn't work with the clock stopped, I think it would be much better to
> have a flag indicating that the clock is stopped, and have the ping function do
> nothing if it is called with stopped clock (ie if suspended).
>
Understood, but I think that corner case should be a common potential issue
in all watchdog drivers which disable clock in suspend with WDOG_HW_RUNNING.
So common way looks better than many different specific flags in such different
watchdog driver with the similar intention?
BTW, for i.mx2_wdt which watchdog can't be stop unless kernel enter into suspend,
that seems like watchdog stop after suspend and clear WDOG_HW_RUNNING makes
sense?
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next prev parent reply other threads:[~2021-05-12 11:37 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-11 11:20 [PATCH v1] watchdog: imx2_wdt: clear WDOG_HW_RUNNING before suspend Robin Gong
2021-05-11 3:59 ` Guenter Roeck
2021-05-12 11:34 ` Robin Gong [this message]
2021-05-12 14:14 ` Guenter Roeck
2021-05-13 3:49 ` Robin Gong
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